Wireless failing to connect

Have you checked how the wireless network is setup / secured on the router. Check to see if you need to enter the remote PCs MAC address to allow connections or see if the router is configured to use WEP encryption in which case your remote PC's wireless card will have to be configured the same with the correct WEP key.

If nopne of this is set then it should be if there are multiple wireless connections in the locality.

Also are you sure the remote PC was actually connecting to the 2100 and not to one of the other wireless networks?